The Department of Chemistry and the Environmental Health Sciences Center (EHSC) at Oregon State University (OSU) request funds to purchase a new high performance MALDI time-of-flight mass spectrometer system. This instrument is needed to accommodate the rapidly growing demand at OSU and the Oregon research community at large for a range of MALDI mass spectrometric analyses. The existing MALDI instrumentation in OSU's Mass Spectrometry Facility does not have the sensitivity, resolving power, mass accuracy, and sample throughput required to support this demand. In particular, the existing instruments are not capable of providing either the quality or quantity of information sought by the investigators designated as major users in this proposal. The new instrument would be used to produce mass- maps of peptides produced by enzymatic and chemical digestion of proteins in efforts to identify the proteins, to obtain sequence tags to aid in the identification of proteins and of sites of phosphorylation or other such modifications within the proteins, to monitor the exchange of hydrogen and deuterium in studies on folding intermediates and conformational states resulting from modifications and ligand interactions, and to monitor the spontaneous deamination of cytosine in double-stranded DNA due to conformational effects. All of these applications would substantially benefit research supported by NIH. Finally, the new mass spectrometer would support a large number of minor users both on- and off-campus who are among those seeking high performance MALDI analysis in their research.